Production Slidessss

7/31/2019 Production Slidessss

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Work

Centre

Cumulative Load

SheetMetal

Electronics

Paint

Hydraulics

A B C D E

A B D

A B C D E

C E

4 21 35 44 55

12 16 42

5 12 24 26 32

12 26

Day

0 55


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Work Centre Capacity

Week Due

1 2 3 4 5 6

Labo

r

hou

rs

For Manual System


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Labo

r

hou

rs

Week Due

1 2

OpenOrders

Planned Orders

Computer-based System

3 4 5 6


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FCFS

Waiting job Processing Time Flow time DueDate

A 4 4 6

B 17 21 20

C 14 35 18

D 9 44 12

E 11 5512

Total Completion time=? Av Flow time=?

Average No of jobs in System= ?

Average job lateness =?


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SPTWaiting job Processing Time Flow time Due

Date

A 4 4 6

D 9 13 12

E 11 24 12

C 14 38 18

B 17 55 20

Total completion time=? Av Flow time=?Av no of jobs in the system each day=? Av job lateness=?


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Predecessor Job

Successor Job

A B C D E

A

B

C

D

E

0

0

0

0

0

29

0

35

15

18

20

14

0

10

16

18

19

37

0

40

24

15

26

10

0

Matrix of Set-up Costs (in dollars)


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Work CentreJob

A B C D E

1

2

4

5

17

7

14

12

9

2

11

6

Processing Times for jobs at two work centers


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A C

A

B

C

E

B

D

E D

WorkCentre: 1

WorkCentre :2

Time0 4 9 18 30 35 42 46 52 55 57

Job flow for sequencing five jobs in two centers in sequence A-C-B-E-D


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Case of Hi-Speed Machining Co.

Hi-Speed Machining Co. has receivedtwo job orders A and B, both of whichrequire processing at machines 1 and2 . First come first serve rule is used

to sequence the jobs: job A arrived inadvance of job B. The sequence ofroutings for the two jobs, both ofwhich are due in 8 hrs. is given . Eachmachine is available for 8 hrs every

day and no other jobs are currentlyscheduled for them . Develop forwardand backward schedules for theoperations


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Scheduling jobs

Route Sheet: Job A Route Sheet: job B

Seqence Machine P Time Seqence Machine P Time

1 1 2 1 1 2

2 2 3 2 2 3

3 1 1

Total 6 Total 5


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0

11

2

3

4

55

6

7

8

A1

B1

A2

B2

A3

M1 M2

A3

A1

B1

B2

A2

B2

M1 M2

Forward Schedule Backward Schedule

Case of Hi Speed Machines Co.


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Work Design

Method Study/Operational Analysis

ImproveOperations bymore effectiveutilization ofresources

Work Measurement

Improve Control by more

accurate planning,manning, estimating andevaluating performance

Motion Study

Analysis of the motions of anoperator following theprescribed Method

Time Study

Determine amount of Timeallowed for the completionof prescribed task

Developed by GilbrethDeveloped by Taylor

(used to evaluatealternate design/Methods)

( used to findthe fastestmotionsequence)

(Design of Total work Systemcompatible with functionrequirements)


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Work Study Work MeasurementMethod Study

Select the work to bestudied.

Record the present

Method

OperationProcess/ActivityCharts

FlowProcess

Charts

MotionCharts

FilmAnalysisCharts

Select the work to bemeasured

Record where necessary effective andineffective time under existing workconditions

1.Rule of Thumb

2. Historical data Approach

3. Direct time Study

4. Predetermined time Study

Method

5. Using Work Sampling

Standard Time for job


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Method Study- Techniques

Operations Charts-operation charts areused to analyze motion of the right and left hands-reaching , carrying grasping, lifting, positioning andreleasing . A time scale is placed in the middle of chartso as to know the time taken by each hand in performing

an associated motion. These charts are used to studyroutine, repetitive short cycle tasks producing low tomoderate volume products

Activity Charts-these charts segment tasksinto small physical actions ;each action human or

machine is timed . In this way the analyst can easilycompute the percentages of productive and idle time andconcentrate on methods of reducing idle time for workerand machine. These are appropriate for routine,repetitive tasks with worker machine interaction.


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Man- Machine Activity Chart

Picks deck from outputstacker /puts rubber band ondeck

Remove rubber

Pick hopper wt.Place deck inhopperReplace wt.Push start button

Opticalscanner readsdeck of cards

Man Machine

IdleTime

IdleTime

Idle

Time


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Flow Process Charts- theseanalyze intersection activities attempting toportray the flow throughout the overallproduction process. Analysts classify themovement of product through theconversion process into one standardcategories: operation transportationstorage inspection delay. Flow charts areused for visualizing the sequential stages ofthe conversion process. They also help toreveal unnecessary or duplicate effortswhose elimination can improve efficiency


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Film Analysis Charts: theseuse filming techniques to record

activity for analysis of the workmethod


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Motion Charts:- These are used foranalyzing and improving workarrangements , the use of human hand and

body or the use of tools to enhance humanefficiency and reduce fatigue. These arebased on law of motion economy- using thehuman body the way it works the best these are broad set of guidelines(given byProf Gilberth focusing on workarrangements , use of human hands andbody, and use of tools


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Motion Study- Laws

To arrange work so that a natural rhythmcan become automatic

Symmetry of body should be considered,

motions of arms should be simultaneous ,completing motions at the same time;shold be opposite and symmetrical

Full capability of human must be emploed;

hands should not be idle ; distribute workto other parts of the body; safe designlimits of the body should be obseved


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Arms and hands as weights are subject tophysical laws and energy should beconserved; movements should not workagainst the body but for the body; smooth

continuous arc of ballistics most efficient;movements should be minimized tasksshould be turned over to machines

Tasks should be simplified-unnecessaryactions, delays and idle time should be

eliminated ; individual motions should beminimized; degree of required precisionand control should be minimized


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Work Measurement

What is an average worker?

What dimension of performanceshould be measured and in whatunits?


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Average Worker?

People differ in their work pace, thatis why to determine a labour std. weneed average worker.

A sample of workers are observedand performance measured. Largesample lead to additional sampling

costs but more accurate averageperformance


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The standard be the performance ofthe average worker or should the std.be set so that every one can beexpected to achieve it?


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example

No. Performance frequency cumulative Freq. Compl. Cum.Units/hr freq.

5 10-14 .05 .05 .95

20 15-19 .20 .25 .75

45 20-24 .45 .70 .30

25 25-29 .25 .95 .05

5 30-34 .05 1.0 0.0


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Performance Dimensions

Sometimes mgt. considers quantity ofinput as primary dimension ofperformance to be measured egpieces sawed per hr/ customer servedper hr. Those related to quality ofinput are secondary e.g. allowable

defective units


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Contd..

Dimesion must be specified beforethe std is set

Std. and subsequent actualperformance must be measurable


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Work MeasurementTechniques

Informal Methods

Historical Data Approach

Time Study approachPredetermined time study approach

Work sampling

Combination approaches


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Informal Methods

Especially in the service sector labourstd are not set. In the light of poorlydefined std. workers are sometimes

criticized for poor performance

Since std are not set, employees settheir own std. by default


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Historical Data Approach

It is based on the assumption thatpast performance is normalperformance. In the absence of other

formal application of techniques Mnymanagers use past performance astheier main guide for setting

standards


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Direct Time Study

Most widely used technique forestablishing work standards inmanufacturing . The steps are:-

1. Select the job to be timed. Workerdoing the job should be should be

repersentative of all workers doingthe job.


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2. select a job cycle. Determine theelements and tasks that constitute acomplete cycle. Decide how many

cycles you need to time with astopwatch

3. Time the job for all cycles and ratethe worker. Assign the worker a

rating as a percentage of normal oraverage worker


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4. compute normal time based onaverage cycle time and worker rating

5. Determine fraction of timeavailablemaking allowances forpersonal needs, delays and fatigue.

6. set std time based on normal time

and the allowances(step 4 and 5)


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Av cycle time = sum of cycle timesrecorded/ No. of cycles observed

Normal Time-Av cycle time* Worker rating

Allowance fraction=fraction of time forpersonal needs/fatigue/ unavoidable delays

Av fraction of time=1-allowance fraction

Std Time=Normal Time/Av fraction of time


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Predetermined Time Study

A technique that involves observing orthinking through a job , recording jobelements, recording pre- establishedmotion units, and calculating a performance

standard

Steps involved are:-

1. Observe the job or think it through undertypical conditions: machines, materials,worker


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2. itemise job elements; thoroughlydocument all motions performed by worker

3. From a table of predetermined time std.

record std time for each motion unit.(therblings)

4. find sum of sid for all motions

5. estimate allowancws for personal time,

delay and fatigue add to sum of std. Thistotal sum is PDTS for the job

Advantage is that times are not skewed


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Example of PDTS Technique

Right Hand TMU Left Hand14.2 Reach to cards3.5 Grasp a card

10.6 Apply pressure to separate

3.5 Turn Card13.4 Move to focus eyes

Transfer card from other hand 5.6

Total 50.8

*6

------

304.8-------


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Work Sampling

It involves defining the state ofworking, observing the jobovertime, and computing the portion

of time the worker is working

Steps are:--

1. Decide what activities are defined asworking/ non working


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2. Observe worker at specific intervals,recording whether a person is working ornot.

3. Calculate proportion of time P a worker isworking

P= No of observations during which workoccurred/Total no. of observations

This calculation can be used as a performancestd.


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example

Day No of Obs. No of Obs. working

Mon 16 8

Tue 15 8

Wed 20 12Thur 16 10

Fri 16 10

83 48

P = 48/83= .578


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Normal Time=(Total observationtime*% of time worker was observedworking* worker rating)/No of units

produced


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Combination Techniques

In Many techniques can be used in

combination for better std.

Documents

Production Slidessss